In a hydraulic system which comprises a working cylinder and a supply conduit disposed between a pump and the working cylinder for supplying hydraulic fluid at high pressure within a predetermined interval, the piston rod of the working cylinder performs a rapid stroke, causing a large flow of hydraulic fluid to be produced, which is pressed out of the working cylinder from its piston side into a low-pressure accumulator for temporary collection therein until said piston rod reverses to perform a slower stroke. Such a low-pressure accumulator operates with a gas chamber which is placed under relatively high pressure and it must therefore be designed in accordance with stipulated standards for pressure vessels with associated need to be approved for use as a pressure vessel. Another drawback is that gas may leak from the gas chamber, mixing with the hydraulic fluid and causing disturbance in operation.